If you liked it, you should buy it. If not, you should still buy it, because it's still a great game. Of course, the choice is yours, but only as long as it's a yes. More seriously, there is no release date for DiRT Rally2 (or even confirmation of its existence). As for repurchasing DiRT Rally, I'd recommend it but ultimately it's your money and your choice: you should only really buy a game if you want to play it. Though, of course, you knew that already. If you want to but don't want to pay full price, you could always wait for a sale, but again, it's up to you, as you already know.
Lol cool I'll probably buy another one. Wouldn't mind if a steelbook pops up for sale!